Electron probe specimen stage with a scattered electron detector mounted thereon

ABSTRACT

A scattered electron detection device for detecting secondary electrons and reflected electrons, characterized in that a scintillator element of the detection device is moved by means of a transferring mechanism which is movable in association with movements of a specimen stage finely movable in two directions in a horizontal plane, in such a manner that the transferring mechanism is moved following movements of the specimen stage in one of the directions but is held against movements of the specimen stage in the other direction orthogonal to said one direction.

States atent 3,629,579

[72] inventor Hideo Naltou [56] References Cited Milo-1M, hm UNITEDSTATES PATENTS {2 l @5 1 mo 3,472,997 l0/l969 Kareh 250/495 A PatentedDec 21,1971 3.509335 4/1970 Nlxon 250/495 B [73] Assignee Hitachi, Ltd.Primary Examiner-James W. Lawrence Tokyo, Japan Assistant Examiner-C. E.Church Attorney-Craig, Antonelli and Hill [54] ELECTRON PROBE SPEClMENSTAGE WITH A SCATTERED ELECTRON DETECTOR MOUNTED ABSTRACT: A scatteredelectron detection device for detect- THEREON ing secondary electronsand reflected electrons, characterized 14 Claims, 15 Drawing Figs. inthat a scintillator element of the detection device is moved by means ofa transferring mechanism which is movable in as- [52] Cl sociation withmovements of a specimen stage finely movable [5 1] at 37/20 in twodirections in a horizontal plane, in such a manner that {50] Fieid"250/49 5 A the transferring mechanism is moved following movements of49.5 B, 49.5 PE, 49.5 P

the specimen stage in one of the directions but is held againstmovements of the specimen stage in the other direction orthogonal tosaid one direction.

PATENTEU E821 um SHEET 1 [1F 9 F/G' PR/Of? ART INVENT OR HIDEO NAI Tau immv ATTORNEY PATENTED EH22! I91! SHEET 2 OF 9 FIG. 2

INVENTOR #1020 NAITOH l W, i w M ATTORNEYS mama; 09:21 m 3629579 SHEET 30F 9 INVENTOR HIDEO NAIToq W' M q M ATTORNEYS PATENTED GU12] 12m 3629579sum u [1F 9 INVENTOR H D NAIToq l M V M I ATTORNEYS PATENTEU DECZI an$529579 sumsore PR/OR ART INVENTOR rosa NAITDQ L 7 W MC! M ATTORNEYSPATENTED BEBZI I97! 3.629579 SHEET 7 0F 9 FIG. 8

from semi/afar INVENTOR PATENTED BEIIZ I BTI SHEET 8 BF 9 INVENTORf/IOEO NAITOH a W M ATTORNEYS PATENIEUIEZIEm 3629579 SHEET 9 OF 9INVENTOR HIDEd NHI'TOM W MMW ATTORNEYJ ELECTRON PROBE SPECIMEN STAGEWITH A SCATTERED ELECTRON DETECTOR MOUNTED THEREON This inventionrelates to a scattered electron detection device for electron-beamirradiating apparatus which analyzes a specimen qualitatively orquantitatively by bombarding an electron beam onto the surface of thespecimen with an electron probe thereby to detect the resulting X-rays,scattered electrons such as secondary electrons and reflected electrons,and the like which contain information on the structure of the specimens surface.

More particularly, the invention relates to a scattered electrondetection device for detecting secondary electrons and reflectedelectrons, for such electron-beam irradiating apparatus as a scanningelectron microscope and an electron probe microanalyzer.

In electron-beam irradiating apparatus such as the scanning electronmicroscope and the electron probe microanalyzer, the surface of aspecimen to be analyzed is irradiated with or scanned by an electronbeam of small diameter. There are thereby detected X-rays as well asscattered electrons such as reflected electrons and secondary electronswhich all contain information on the surface topography of the specimen.Thus information on the topography of the specimen's surface may beobtained, the state of distribution of a specific element constitutingthe specimen and the potential distribution of semiconductors, etc.

Usual SEM (scanning electron microscope) and an EPM (electron probemicroanalyzer) are provided in the vicinity of a specimen with adetector system comprising a plurality of detectors for simultaneouslydetecting, through electronbeam bombardment onto the specimen, certaininformation such as the primary reflected electrons, secondary emittedelectrons, X-rays and electrons absorbed by the specimen.

In order to select an area to be analyzed on the specimen's surface, aspecimen stage on which the specimen is placed is movable in twoorthogonal traversing directions in a horizontal plane and the specimenunder the electron beam is rotatable about the axis of the electronbeam. In addition, for focusing of an optical microscope, the specimenstage is adapted to move up and down along a column axis.

The detector system and the specimen moving system should be disposed inthe vicinity of the specimen, while an obiective electron lens shouldhave the least possible focal length in order to minimize sphericalaberration. Therefore, the space between the bottom surface of theobjective electron lens and the specimen surface on the specimen stagecannot but be restricted to the extreme.

In view of the above circumstances, the detector system has hithertobeen equipped outside the movable range of the specimen moving system.Particularly, the scattered electron detection device for detectingreflected electrons and secondary electrons from the specimen has beenfixedly equipped at a part of the column outside the movable range ofthe specimen stage, so that it has been difficult to efficiently detectscattered electrons from the electron-beam irradiated area on thespecimen surface. Particularly the secondary electrons have considerablylower energy than the reflected electrons, so that various expedientsheretofore made for the efficient collection of the former electronshave, in no case, achieved satisfactory effects due to the spacelimitation as mentioned above.

It is accordingly the first object of the invention to provide a new andimproved scattered electron detection device wherein ascattered-electron a scintillator element and a photoelectric element ismounted on a specimen stage finely movable in two directions in ahorizontal plane and thereby said detector is caused to follow themovement of the specimen stage to always bring the scattered-electronincident surface of the scintillator element of said detector to face anelectron-beam irradiated area on the specimen surface, whereby scatteredelectrons may be efficiently collected even within a restricted space.

The second object of the invention is to provide a scattered electrondetection device wherein a scintillator element of the detection deviceis moved by means of a transferring mechanism movable in associationwith the movements of a specimen stage finely movable in two directionsin a horizontal plane, in such a manner that the transferring mechanismis moved following movements of the specimen stage in one of thedirections but is held against movements of the specimen stage in theother direction orthogonal to said one direction, whereby irrespectiveof the moved position of the specimen stage, the incident surface ofscattered electrons upon the scintillator element may always be broughtto face an electron-beam irradiated area on the specimen surface, andsimultaneously, the relative distance between the electron-beamirradiated area and the scintillator element may be kept approximatelyconstant.

The third object of the invention is to provide a scattered electrondetection device wherein only a scintillator element of the detectiondevice is attached to a transferring mechanism which is movable inassociation with movements of a specimen stage finely movable in twodirections in a horizontal plane, in such a manner that the transferringmechanism is moved following movements of the specimen stage in one ofthe directions but is held against movements of the specimen stage inone of the directions but is held against movements of the specimenstage in the other direction orthogonal to said one direction andwherein the scintillator element and a photoelectric element disposed ata part of a column outside the movable range of the specimen stage areconnected by means of a flexible fiber optics bundle such as glassfiber, whereby scattered electrons may be efficiently detected withoutbeing subject to any spatial limit.

The fourth object of the invention is to provide a scattered electrondetection device wherein a positively biased auxiliary electrode forcollecting secondary emitted electrons is equipped at that part of theaforementioned transferring mechanism facing the electron-beamirradiated area, whereby under the resultant action with an electricfield due to a positive voltage applied to a secondaryelectron-collecting electrode disposed at the scintillator element,particularly secondary electrons of low energy may be efficientlydetected.

The fifth object of the invention is to provide an electron probemicroanalyzer having a higher resolution than in the prior art, saidelectron probe analyzer being provided with a scattered electrondetection device which follows, in a determined relation, movements of aspecimen stage. Further objects of the invention will become apparentwith reference to the following description taken in conjunction withthe accompanying drawings, in which:

FIG. 1 shows a partly schematic, vertical, sectional view of a prior artscattered electron detection device applied to an electron probemicroanalyzer;

FIG. 2 shows a partly schematic, vertical, sectional view of a scatteredelectron detection device of one embodiment of the present inventionapplied to an electron probe analyzer;

FIG. 3 illustrates a perspective view, partly in section, of anotherembodiment of the invention;

FIG. 4 depicts a side view, partly in longitudinal section, of FIG. 3;

FIG. 5 depicts a plan view of FIG. 3;

FIG. 6 depicts a front view of FIG. 3;

FIG. 7a illustrates a diagram of the distribution of electric field by apositive voltage applied to a secondary-electron collecting electrodedisposed at a scintillator element in the prior art device shown in FIG.1,

FIG. 7b illustrates a diagram of the distribution of electric fieldbased upon a positive voltage applied to a secondaryelectron collectingelectrode disposed at a scintillator element in the embodiment shown inFIG. 3 and upon a further positive voltage applied to asecondary-electron collecting auxiliary electrode disposed at a part ofa transferring mechanism;

FIG. 8 illustrates a scintillator element and a photoelectric conversionelement which are connected to each other with a flexible fiber opticsbundle in the embodiment shown in FIG 3;

FIGS. 9a to 9e are diagrams for illustrating of the relativerelationship between the scintillator element in the embodiment shown inFIG. 3 and electron-beam irradiated areas on a specimen; and

FIG. 10 shows a schematic view wherein the embodiment shown in FIG. 3 isapplied to an electron probe microanalyzer.

A scanning electron microscope as well as an electron probemicroanalyzer qualitatively or quantitatively analyze a specimen byscanning two-dimensionally an area to be analyzed on the specimensurface with a demagnified electron beam (having a diameter of 1p. orless) and by detecting the resultant X-rays scattered electrons(I-Iereinbelow the expression scattered electrons shall mean reflectedelectrons and secondary electrons at least and shall not mean so-calledstray electrons which become a cause of a background. etc.

In the detection, the scattered electrons are incident upon ascintillator element disposed in the vicinity of the specimen, and areconverted into light therein. This light is conducted to a photoelectricelement such as a photomultiplier tube, wherein the incident light isconverted into an electrical signal proportional thereto.

In the prior art, the scattered electron detection device for detectingsecondary electrons and reflected electrons has been disposed, as shownin FIG. 1, at a part of a column outside the movable range of a specimenstage and in the vicinity of the specimen stage. More particularly,referring to the figure, the reference numeral 1 designates the specimenstage which may be finely moved in two directions in a horizontal plane,while 2 a disk-shaped specimen selector which is finely movable in twodirections in a horizontal plane in accordance with the movement of thespecimen stage 1 and which is also rotatable about an axis 3 independentof the movement of the specimen stage 1. On the specimen selector areprovided a plurality of specimen holders 4, each of which is placedthereon with a specimen 5 to be analyzed. A specimen holder 4 located inthe analysis position under an electron beam 6 may be rotated about anaxis 7 independent of the movements of the specimen stage 1 and thespecimen selector disk 2. In order to focus reflection objective minors8 and 9 of an optical microscope, a specimen moving system comprisingthe specimen stage I and the disk-shaped specimen selector 2 may bevertically moved up and down along a column axis (which agrees with theaxis of the electron beam 6). Numeral I0 indicates an objective electronlens, and numeral 11 represents a deflection coil for two-dimensionallydeflecting the electron beam. At 12 is designated the scattered electrondetector, which comprises a scintillator element 13 and aphotomultiplier tube 14 and which is fixed at a part of the columnoutside the range of movement of the specimen moving system, by means ofa mounting frame 15.

The electron beam 6 (being 1 p. or less in diameter) demagnified by theobjective electron lens is irradiated onto the surface of the specimen 5on the specimen holder 4. The electron beam is deflected by means of thedeflection coil 11, and thereby scans the surface of the specimen 5 intwo dimensions. Scattered electrons resulting from the beam scanning areincident upon the scintillator element I3. Among the: scatteredelectrons, primary electrons reflected from the specimen have, ingeneral, high energy and hence are rapidly emitted from out of thespecimen surface straightforward or linearly due to electron-beambombardment onto the specimen surface. In contrast, secondary electronshave lower energy than reflected electrons, so that the former electronsare attracted to the scintillator element 13 under the action of anelectric field for collecting secondary electrons, the electric fieldbeing based on a positive voltage applied to a secondary-electroncollecting electrode usually provided for the scintillator element 13.In the above case, in order to select a spot to be analyzed on thesurface of the specimen 5, such a desired spot for analysis is broughtunder the electron beam 6 by finely moving the specimen stage 1 in twodirections in a horizontal lane. P When the scattered electron detector12 is located, as shown in FIG. 1, outside the range of movement of thespecimen moving system comprising the specimen stage I and the specimenselecting disk 2, a movement of the specimen stage 1 in the direction ofX or X the specimen holder 4 on which the specimen to be analyzed isplaced will be displaced to a position of 4' or 4", whereby the relativedistance between the specimen 5 and the scattered electron detector 12is changed. As a result, the electric field on the basis of the positivevoltage for the secondaryelectron collection as applied to thescintillator element 13 is not sufl'iciently extended, and it becomesdifficult to efficiently collect secondary electrons with lower energy.

In case where the specimen stage 1 is moved in the directions of Y and Ywhich are orthogonal to the X- and X'- senses, the relative directionbetween the specimen 5 and the scintillator element 13 is changed.Therefore, the prior art has been disadvantageous in the analysis of avery small area in that scattered electrons from the area can not besufficiently collected. In addition, when the surface of the specimen isrough, it has been impossible to satisfactorily detect scatteredelectrons appearing from an area on which the electron beam isirradiated, due to a long distance between the area and the detector.

The aforementioned reasons as well as the disadvantage that thescattered electron detection device for detecting reflected electronsand secondary electrons may not be located at the optimum positionbecause of the space limitation, have been one of the causes fordeterioration of the resolution of a secondary-electron image orreflected-electron image of the specimen displayed on the screen of acathoderay tube.

In contrast, according to the present invention, the scattered electrondetector 12 is fixedly mounted as shown in FIG. 2 at one end of thespecimen stage 1 finely movable in two directions in a horizontal plane,and through a mounting frame 16.

More particularly, upon movement of the specimen stage I in thedirection of the arrow X or X thereby to locate the specimen holder 4 atthe position of 4 or 4" respectively, the scattered electron detector 12is correspondingly moved to the position of 12' or 12" respectively.Accordingly, as is well known it is not required to dispose thescattered electron detector 12 outside the movable range of the specimenmoving system, but it is possible to attach the same much nearer to theelectron beam irradiated area on the specimen 5. In addition, thedetector is also moved in accordance with the movement of the specimenstage, so that the relative distance between the specimen holder 4 andthe scintillator element 13 is not changed. As a result, the electricfield based on the positive voltage applied to the secondary-electroncollecting electrode which is provided for the scintillator element,effectively functions to detect the secondary electrons or reflectedelectrons.

Even when the detector is mounted due to the spatial limitation on suchposition, as shown in FlG. 2, that the scatteredelectron incidentsurface of the scintillator element [3 may not directly face to thedirection of the scattered electrons from the electron-beam irradiatedarea on the surface of the specimen 5, the scattered electrons may beefficiently detected.

Referring now to FIGS. 3 to 6, a further embodiment of the inventionwill be described. Numeral 1 indicates the specimen stage which isfinely movable in two directions in a horizontal plane, while 2 thedisk-shaped specimen selector the upper surface of which is providedwith a plurality of specimen holders 4. Each holder is placed with thespecimen 5 to be analyzed. The specimen moving system comprising thespecimen stage 1 and the disk-shaped specimen selector 2 is moved in thesame manner as in FIG. 1.

At 17 is designated a cylindrical transferring member therein receivingthe scintillator element 13. The transferring member is attached to arail 19 mounted by means of a screw 18 onto the bottom surface of theobjective electron lens I0 in such a manner that said transferringmember may be moved along the rail 19 through rotary members 22 and 23such as ball bearings which are provided on mounting frames 20 and 21and at one end thereof.

The transferring member 17 is connected with the specimen stage 1through a guide 26 which is attached to the mounting frame 20 by meansof a mounting screw 24 and which has a groove 25 and through contact ofa strut 27 provided at one end of the specimen stage 1 with the groove25.

Upon movement of the specimen stage 1 in the X-or X- direction, thetransferring member 17 is moved in the X-or X'- direction respectivelyalong the rail 19 through the guide 26 as well as the strut 27 incontact with the groove 25 formed in said guide.

On the other hand, when the specimen stage 1 is moved in the Y-orY-direction both being orthogonal to X- and X'- directions, the strut 27only slides in the groove 25 of the guide 26, so that the transferringmember 17 is not moved but remains at the position as it is.

The reference numeral 29 designates a meshlike auxiliary electrode forapplication of a positive voltage of +300-+l,000 v. for the collectionof secondary-electrons, the auxiliary electrode 29 being provided on anarm 28 extending at one end of the transferring member 17 towards theelectron-beam irradiated area on the specimen 5. At 13 is indicated thescintillator element, the electron incident surface of which is coatedwith a metallic membrane of, for example, aluminum. A uniform positivevoltage of +12 kv. is applied throughout the metallic membrane through acircular electrode 30 (see FIG. 8) around the electron incident surface.

Represented by 31 is a light guide consisting of a flexible bundle ofoptical fibers of 50;; diameter and having a diameter of 12 mm. Thelight guide 31 connects the scintillator element 13 housed inside thetransferring member 17 and a photoelectric element 32. More detailedexplanation will now be made, with reference to H0. 8. As shown in thefigure, the scintillator element 13 has its circumference surrounded bythe circular electrode 30 for application of the positive voltage, andis housed in the transferring member 17 through an insulating material33. The light guide 31 is received at one end thereof in a shield case34 for shielding light, and is pushed by a spring 35 against the lightreceiving face of the photomultiplier tube 32 which is provided at apart of the column which is not so severely subjected to the spatiallimitation.

Using the construction as described above, the operation and advantagesof this embodiment will now be explained.

FIG. 9a schematically illustrates the relative positions and magnitudesamong the specimen 5 to be analyzed, the scintillator element 13received in the transferring member 17, and areas A, B, scanned by theelectron beam.

As shown in the figure, the specimen 5 is about 32 mm. in diameter, theelectron probe with which the surface of the specimen is irradiated hasa spot size less than In. in diameter, each area on the specimen 5scanned by the electron probe is approximately 2 mm. X 2 mm. in size,and the scattered-electron incident face of the scintillator element 13which collects such scattered electrons excited from the electron-beamscanning area as secondary electrons and reflected electrons isapproximately 12 mm. in diameter. The electron probe scans an area ofapproximately 2 mm. X 2 mm., having its center at point 0. Accordingly,it is required in the analysis to select an area to be analyzed on thespecimen 5 and to bring this area to the electron-beam irradiated areaby suitably finely moving the specimen stage 1. Now description will bemade of the case where areas to be analyzed on the specimen arerepresented by four areas A, B, C and D.

l. The analysis of the A-area will be explained with reference to FIG.9b. In this case, the specimen stage 1, that is, the specimen 5 is movedin the X-direction from the position shown in FIG. 9a to bring theA-area to the electron-beam irradiated area 0. Since the transferringmember 17 is also moved in the X-directions along the rail 19, thefacing relation between the scintillator element 13 and the A-area doesnot change. The relative distance also remains unchanged from thatbefore the movement in the location shown in FIG. 9a.

2. Consider the analysis of the B-area with reference to FIG. 9c. Inthis case, the specimen 5 is moved in the X'-directions thereby to bringthe B-area to the electron-beam irradiated area 0. Similarly to the caseof I, the transferring member 17 is also moved in the X'-direction, sothat the relative relationship and the relative distance respectivelybetween the scintillator element 13 and the B-area are maintainedconstant.

In both the above cases of (l) and (2), the direction in which thespecimen is moved and that in which the scintillator element is movedagree with each other, and hence the electron incident surface of thescintillator element 13 is always facing to the electron-beam irradiatedarea on the specimen. In these cases, therefore, there are accomplishedthe same technical advantages as attained by the first embodimentdescribed with reference to FIG. 2.

3. Description will now be made, with reference to FIG. 9d, of the casewhere the C-area is to be analyzed. In this case, the specimen 5 ismoved in the Y-direction from the state shown in FIG. thereby bringingthe C-area to the electron-beam irradiated area O. This movement,however, only causes the strut 27 disposed at one end of the specimenstage 1 to slide in the groove 25 of the guide 26, and the transferringmember 17 remains at its position where located. More particularly,although the electron incident surface of the scintillator ele ment 13was not so positioned in the state of FIG. 9a as to directly face theC-area, the above operation has caused only the specimen 5 to move inthe Y-sense, with the result that the electron incident surface of thescintillator element 13 has become directly facing opposite to theC-area. Also the relative distance becomes shorter than in FIG. 9a.

4. The analysis of the D-area will now be explained with reference toFIG. 9e. The specimen 5 is moved in the Y sense to bring the D-area tothe electron-beam irradiated area 0. In this case, similarly to the caseof (3), only the specimen 5 is moved in the Y'-direction, with thetransferring member 17 remaining at its position where located.Accordingly, the D- area and the electron incident surface of thescintillator element 13 are directly faced to each other, and therelative distance therebetween becomes shorter when compared with thatin the case of FIG. 9a.

In the above cases of (3) and (4), even when the specimen stage 1 ismoved, the strut 27 only slides in the groove 27 of the guide 26, andthe transferring member 17 and accordingly the scintillator element 13are maintained at their fixed positions without any movement.

Although in the foregoing description the analyses of the four areas ofA, B, C and D have been representatively considered, an analysis of anyother area than mentioned above may be considered by decomposing thedirection of movement into vectors of X- and X'-directions and Y- and Y-directions. Therefore, such decomposed directions becomes identical toeither one of the cases (l)-(4), and such analysis becomes, as aconsequence, a combined case of the individual cases of( l )(4).

As detailed above, according to this embodiment, irrespective of themoved position of the specimen stage 1, that is, the specimen 5 theelectron-beam scanning area on the surface of the specimen and theelectron incident surface of the scintillator element 13 are alwayspositioned to be directly faced. Also, the relative distancetherebetween is kept constant in the cases of (3) and (4). Although saidrelative distance is changed with the distance of movement of thespecimen stage 1 in the cases of (I) and (2), the scintillator element13 is positioned considerably nearer to the electron-beam irradiatedarea on the specimen than in the case where the scattered electrondetection device is equipped outside the movable range of the specimenmoving system. As a result, jointly with the effect of extending theelectric-field distribution due to the secondary-electron collectingelectrodes, particularly the secondary electrons with low energy may bemore efficiently collected.

FIG 7b illustrates the electric-field distribution in the case whereinthe secondary-electron collecting electrode disposed at the scintillatorelement 13 is applied with a voltage of +1 2 kv. while the auxiliaryelectrode 29 disposed at one end of the transferring member 17 isappliedwith a voltage of +800 v. FIG. 7a depicts the electric-fielddistribution in the case wherein in the prior art device shown in anddescribed with reference to FIG 1, a positive voltage of +l2kv. isapplied to the secondary-electron collecting electrode disposed at thescintillator element 13 of the scattered electron detector 12 which isfixed outside the movable range of the specimen moving system. In thiscase, the specimen holder 4 and accordingly the specimen under theirradiation of the electron beam are at ground potential. According tothe second embodiment of the invention, the field distribution on thebasis of the voltages of +12 kv. and +800 v. is developed, as shown inFIG. 712, near to the electron-beam irradiated area on the specimensurface. Thus, the secondary electrons emitted from the above said areainay be more efficiently collected than in the prior art, and theresolution of the secondary-electron image as well as thereflected-electron image of the specimen may be rapidly enhanced. By wayof example, the resolution of a secondaryelectron image obtained wasapproximately 1,000 1,000A. with the prior art device shown in FIG 1,whereas that of the same was rapidly increased to be as high asapproximately 500 A. according to this embodiment.

There has hitherto been used for the scintillator element 13 ascattered-electron incident surface of comparatively large diameter, inorder to enhance the electron-collecting efficiency for the scatteredelectrons within a restricted space. According to this embodiment, sincethe electron incident surface of the scintillator element 13 may bealways faced to the scattered-electron appearing area on the specimensurface, the diameter of the scintillator element used may becomparatively small, which permits an effective utilization of space.

It has heretofore been unavoidable in the case of low electroncollectingefficiency for the scattered electrons to increase the sensitivity ofthe photomultiplier tube by raising the applied voltage between thecathode and anode of said tube for observation of a specimen image. Thishas, however, been disadvantageous for detection of small signals sincenoises due to the dark current etc. of the photomultiplier tube havealso been increased. In accordance with this embodiment, since thescattered-electron collecting efficiency has been further increasedrelative to the prior art, the cathode-anode applied voltage of thephotomultiplier tube may be reduced. Accordingly, noises may also bereduced, so that the invention is more advantageous for detection ofsmall signals.

FIG. is a schematic view showing an electron probe microanalyzer towhich the scattered electron detection device embodying the inventionand shown in FIG. 3 is attached. In the figure, the reference numeral 36designates an electron gun. An electron beam 6 from the electron gun isdemagnified by a first condenser lens 37 and a second condenser lens(objective lens) 10, and is thereby focused onto the surface of aspecimen on the specimen holder 4.

At 1 is designated the specimen holder finely movable in two directionsin a horizontal plane and at 2 is represented the disk-shaped specimenselector rotatable about the axis 3, and these two members may berespectively operated by knobs 40 and 41 from outside the vacuum system.The specimen holder 4 thereon placed with specimens may be rotated, whenlocated in the analysis position under the electron beam, about the axis7 by operating a knob 42 from outside vacuum. ln addition, the specimenstage 1 and the specimen selecting disk 2 may be integrally moved up anddown along the column axis through operation of a knob 43 from outsidevacuum, in order to focus the optical microscope.

The optical microscope consists of a light source 39, a flat mirror 38,objective reflection mirrors 8 and 9, and a magnifier 39.

The scattered electron detection device comprises a transferringmechanism which follows movements of the specimen stage 1 in theabove-mentioned relation and which receives the scintillator elementtherein, the light guide 31 including flexible optical fibers, and thephotoelectric element 32 such as a photomultiplier tube which is fixedat a part of the column outside the movable range of the specimen movingsystem consisting of the specimen stage 1 and the specimen selector disk2.

The electron probe microanalyzer has its primary object in detectingX-rays generated by bombarding the electron beam onto the specimen,thereby to analyze the specimen qualitatively or quantitatively.Therefore, it is required that the surface of the specimen be locatednormal to the electron beam axis. Still, even in case where it is verydifficult to attach the secondary-electron detection device due torestrictions in space or where it is unavoidable to disposed saiddetection device at such position between the bottom surface of theobjective electron lens and the specimen holder as shown in FIG. 10 thatthe electron incident surface of the scintillator element is notdirectly faced in a direction of secondary-electrons emitted from theelectron-beam irradiated area on the specimen surface, the secondaryelectrons may be efficiently collected owing to the electric-fielddistribution due to positive voltages applied to the transferringmechanism and the secondary-electron collecting electrodes.

In the above embodiments, description has been made of the cases whereinthe scattered electron detection device is in any case subject to thespatial limitation and it is disposed at such position between a lowerpart of the objective electron lens and the specimen holder on thespecimen stage that the scattered-electron incident surface of thescintillator is not directly faced in the direction in which thescattered electrons appear from the electron-beam irradiated area on thesurface of the specimen. The invention, however, is not restricted tothe foregoing embodiments, buy may of course be applied to the casewhere the scattered-electron incident surface of the scintillator isfaced directly towards to where the scatteredelectrons appear directionfrom the electron-beam irradiated area on the specimen surface-forexample, where the surface of the specimen is inclined with respect tothe electron beam axis. In this case, primary reflected electrons may bemainly detected by maintaining at the ground potential the acceleratingelectrode disposed on the surface of the scintillator and the auxiliaryelectrode disposed at the extreme end of the transferring mechanism,while secondary emitted electrons may be detected by applying positivevoltages to the electrodes.

What is claimed is:

1. An apparatus for bombarding a specimen with an electron-beam anddetecting scattered electrons produced by the bombardment, comprising anelectron gun; and objective electron lens for focusing an electron beamfrom said electron gun onto a selected area for analysis on thespecimen; specimen moving means to move the specimen in two directionsin a horizontal plane; transferring means responsive to movements ofsaid specimen-moving means for following the movement of said movingmeans in one of the two directions and for holding a fixed positionthereof during movement in the other direction orthogonal to said onedirection; a scintillator element upon which impinge scattered electronsfrom said selected electron-beam irradiated area on the specimen, saidscintillator element being mounted on said transferring means; and aphotoelectric element for convert ing light produced by saidscintillator element into an electric signal proportional to said light.

2. An apparatus for bombarding a specimen with an electron beam anddetecting scattered electrons produced by the bombardment, comprising anelectron gun; an objective electron lens for focusing an electron beamfrom said electron gun onto a selected area for analysis of thespecimen; specimen moving means to move the specimen in two directionsin a horizontal plane; transferring means responsive to movements ofsaid specimen moving means for following the movement of said movingmeans in one of the two directions and for holding a fixed positionthereof during movement in the other direction orthogonal to said onedirection; a scintillator ele ment upon which impinge scatteredelectrons from said selected electronlbeam irradiated area on thespecimen, said scintillator element being mounted on said transferringmeans; a photoelectric element fixed at a part of a column outside themovable range of said specimen moving means; and a light guide includingflexible optical fibers for conducting light produced by saidscintillator element to said photoelectric element.

3. An electron probe microanalyzer comprising an electron gun; andobjective electron lens for focusing an electron-beam from said electrongun onto a selected area for analysis on the specimen; specimen-movingmeans to move the specimen in two directions in a horizontal plane;transferring means responsive to movements of said specimen moving meansfor following the movement of said moving means in one of the twodirections and for holding a fixed position thereof during movement inthe other direction orthogonal to said one direction; a scintillatorelement attached to said u'ansferring mechanism and coated on thesurface thereof with a metallic membrane; means to apply a positivevoltage to said scintillator element and being disposed therearound; anauxiliary electrode attached at one end of said transferring meansfacing said selected electron-beam irradiated area on the surface of thespecimen, said auxiliary electrode producing an electricfielddistribution in the area of said specimen due to said positive voltageapplying means being connected thereto; a photoelectric element fixedoutside the movable range of said specimen moving means; and a lightguide including flexible optical fibers for conducting light produced bysaid scintillator element to said photoelectric element.

4. An electron beam apparatus comprising:

an electron beam source,

an electron beam condenser lens system comprising at least one condenserlens for demagnifying and focusing the electron beam from said sourceonto the specimen to be analyzed,

specimen-mounting means carrying the specimen for movement in twodirections orthogonal to each other in a plane perpendicular to saidelectron beam, moveable electron detector means having an electronincident surface for detecting electrons received from said specimen dueto the irradiation of the electron beam, and

holding means coupling movement of said electron detector means tomovement of said specimen mounting means for holding said electronincident surface of said detector means and the irradiated area of thespecimen in a predetermined opposing relationship.

5. An electron beam apparatus as claimed in claim 4, wherein saidelectron detector means comprises a scintillator element for collectingthe electrons advanced from said electron-beam irradiated area of thespecimen and a photoelectric element for converting light generated bysaid scintillator element into electrical signals proportional to saidlight, and said holding means comprising means for directly connectingsaid detector means to said specimen mounting means.

6. An electron beam apparatus as claimed in claim 4, wherein saidelectron detector means comprises a scintillator element for collectingthe electrons advanced from said electron-beam irradiated area of thespecimen, and said holding means comprises a transferring casing memberengaged at a bottom part of the last stage condenser lens of said lenssystem in the vicinity of said specimen mounting means, said casingmember accommodating therein said scintillator element and being movablein parallel with one of said two directions of movement of said specimenmounting means, and means for movably engaging said casing member tosaid specimen mounting means to move said member in accordance withmovement of said specimen mounting means in said one direction and tohold said member against movement of said specimen mounting means in theother direction of said two orthogonal directions; said apparatusfurther comprising a photoelectric element for converting light producedby said scintillator element into electrical signals proportional tosaid light.

7. An electron beam apparatus as claimed in claim 4, wherein saidelectron detector means comprises a scintillator element for collectingthe electrons advanced from an electron-beam irradiated area of thespecimen and a photoelectric 5 element for converting light generated bysaid scintillator element into electrical signals proportional to saidlight; said holding means comprising a transferring casing memberengaged at a bottom part of the last stage condenser lens of said lenssystem in the vicinity of said specimen mounting means, said casingmember accommodating therein said scintillator element and saidphotoelectric element and being movable in parallel with one of said twodirections of movement of said specimen mounting means, and means forengaging said casing member to said specimen mounting means to move saidmember in accordance with movement of said specimen mounting means insaid one direction and to hold said member against movement of saidspecimen mounting means in the other direction of said two orthogonaldirections.

8. An electron beam apparatus as claimed in claim 7, further comprisinga light guide composed of flexible optical fibers for conducting thelight generated by said scintillator element to said photoelectricelement, wherein said photoelectric element is secured to saidapparatus.

9. A electron beam apparatus as claimed in claim 6, wherein saidscintillator element includes a metal film coating which forms saidelectron incident surface of said detector means; and said detectormeans further comprises means to apply a first positive voltage to saidscintillator element and being disposed therearound and an auxiliaryelectrode being fed at a second positive voltage and being attached atone end of said transferring casing member so as to oppose saidelectronbeam irradiated area of the specimen, said auxiliary electrodeproviding an electric-field distribution due to the first positivevoltage of said scintillator.

10. An electron beam apparatus as claimed in claim 7, wherein saidtransferring casing member is located above said specimen mounting meansand below said last stage condenser lens system and on a side of saidspecimen mounting means at a certain distance therefrom, so that saidelectron incident surface of said scintillator element does not directlyface the irradiated area of the specimen.

11. An apparatus for bombarding a specimen with an electron-beam anddetecting secondary electrons generated by the bombardment: comprisingan electron gun;

condenser lens means for focusing the electron beam from said electrongun onto a selected area for analysis of the specimen surface, said lensmeans being disposed as close as possible to the specimen for shorteningthe focal length of the lens;

a specimen stage movable in two directions perpendicular to each otherin a plane perpendicular to said beam;

a transferring member movably engaged to a bottom part of said condenserlens means in the vicinity of said specimen stage so as to becomemovable in parallel with one of said two directions;

means for engaging said transferring member to said specimen stage tomove said member in accordance with movement of said specimen stage inone of said two directions and to hold said member against movement ofsaid specimen stage in the other direction;

a scintillator element mounted on said transferring member forcollecting incident electrons from the electron-beam irradiated area ofthe specimen;

and a photoelectric element connected to said scintillator element forconverting light produced by said scintillator element into an electricsignal proportional to said light.

12. An apparatus for bombarding a specimen with an electron-beam anddetecting secondary electrons generated by the bombardment, comprisingan electron gun;

condenser lens means for focusing the electron beam from said electrongun onto a selected area for analysis on the specimen surface, said lensbeing disposed as close to the specimen as possible for shortening thefocal length of the lens; 4

a specimen stage movable in two perpendicular directions in a planeperpendicular to said beam;

transferring means movably engaged to a bottom part of said condenserlens means in the vicinity of said specimen stage so as to becomemovable in parallel with one of said two directions;

means for engaging said transferring means to said specimen stage tomove said transferring means in accordance with movement of saidspecimen stage in one of said two directions and hold said transferringmeans against movement of said specimen stage in the other direction;

a scintillator element mounted on said transferring means for collectingincident electrons from the electron-beam irradiated area of thespecimen;

a photoelectric element secured on said apparatus for converting lightproduced by said scintillator element into an electric signalproportional to said light;

and a light guide including flexible optical fibers for conducting lightproduced by said scintillator element to said photoelectric element.

13. An apparatus as claimed in claim 11, wherein said scintillatorelement is of a metal film coating which forms said electron incidentsurface of said detector means, further comprising means to apply afirst positive voltage to said scintillator element and being disposedtherearound and an auxiliary electrode being fed at a second positivevoltage attached at one end of said transferring means and opposing saidelectronbeam irradiated area of he specimen, said auxiliary electrodeproviding an electric-field distribution by the first positive voltageof said scintillator.

14. An apparatus as claimed in claim 12, wherein said transferring meanscomprises cylindrical casing having mounting frames secured therearoundand ball bearing rotary members respectively attached to the frames, andrail means attached in parallel with said one of said two directions tosaid bottom part of said condenser lens means and receiving therein saidrotary members whereby said cylindrical casing can travel along saidrail means; and said engaging means comprises a U- shaped guide memberdefining a guide groove and secured in parallel with said otherdirection to one of said frames, and a strut member disposed on aperipheral part of said specimen stage and slidably engaged in the guidegroove of said U- shaped member.

ommmeunm- Patent No. Dated December 21, 197i it is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Priority data should read:

Japan, 4243/69, filed January 20, 1969, and

Japan, 67386/69, filed August 25, 1969--.

Signed and sealed this 29th day of May 1973.

(SEAL) Attest:

EDWARD M.PLETCHER,JR ROBERT GOTTSCHALK Attestlng Officer Commissioner ofPatents FORM PC4050 (10-69) USCOMM-DC 6O376-P69 u.s. GOVERNMENT PRINTINGOFFICE: I969 0-366-331 Mr A v A A V

1. An apparatus for bombarding a specimen with an electron-beam and detecting scattered electrons produced by the bombardment, comprising an electron gun; and objective electron lens for focusing an electron beam from said electron gun onto a selected area for analysis on the specimen; specimen moving means to move the specimen in two directions in a horizontal plane; transferring means responsive to movements of said specimenmoving means for following the movement of said moving means in one of the two directions and for holding a fixed position thereof during movement in the other direction orthogonal to said one direction; a scintillator element upon which impinge scattered electrons from said selected electron-beam irradiated area on the specimen, said scintillator element being mounted on said transferring means; and a photoelectric element for converting light produced by said scintillator element into an electric signal proportional to said light.
 2. An apparatus for bombarding a specimen with an electron beam and detecting scattered electrons produced by the bombardment, comprising an electron gun; an objective electron lens for focusing an electron beam from said electron gun onto a selected area for analysis of the specimen; specimen moving means to move the specimen in two directions in a horizontal plane; transferring means responsive to movements of said specimen moving means for following the movement of said moving means in one of the two directions and for holding a fixed position thereof during movement in the other direction orthogonal to said one direction; a scintillator element upon which impinge scattered electrons from said selected electron-beam irradiated area on the specimen, said scintillator element being mounted on said transferring means; a photoelectric element fixed at a part of a column outside the movable range of said specimen moving means; and a light guide including flexible optical fibers for conducting light produced by said scintillator element to said photoelectric element.
 3. An electron probe microanalyzer comprising an electron gun; and objective electron lens for focusing an electron-beam from said electron gun onto a selected area for analysis on the specimen; sPecimen-moving means to move the specimen in two directions in a horizontal plane; transferring means responsive to movements of said specimen moving means for following the movement of said moving means in one of the two directions and for holding a fixed position thereof during movement in the other direction orthogonal to said one direction; a scintillator element attached to said transferring mechanism and coated on the surface thereof with a metallic membrane; means to apply a positive voltage to said scintillator element and being disposed therearound; an auxiliary electrode attached at one end of said transferring means facing said selected electron-beam irradiated area on the surface of the specimen, said auxiliary electrode producing an electric-field distribution in the area of said specimen due to said positive voltage applying means being connected thereto; a photoelectric element fixed outside the movable range of said specimen moving means; and a light guide including flexible optical fibers for conducting light produced by said scintillator element to said photoelectric element.
 4. An electron beam apparatus comprising: an electron beam source, an electron beam condenser lens system comprising at least one condenser lens for demagnifying and focusing the electron beam from said source onto the specimen to be analyzed, specimen-mounting means carrying the specimen for movement in two directions orthogonal to each other in a plane perpendicular to said electron beam, moveable electron detector means having an electron incident surface for detecting electrons received from said specimen due to the irradiation of the electron beam, and holding means coupling movement of said electron detector means to movement of said specimen mounting means for holding said electron incident surface of said detector means and the irradiated area of the specimen in a predetermined opposing relationship.
 5. An electron beam apparatus as claimed in claim 4, wherein said electron detector means comprises a scintillator element for collecting the electrons advanced from said electron-beam irradiated area of the specimen and a photoelectric element for converting light generated by said scintillator element into electrical signals proportional to said light, and said holding means comprising means for directly connecting said detector means to said specimen mounting means.
 6. An electron beam apparatus as claimed in claim 4, wherein said electron detector means comprises a scintillator element for collecting the electrons advanced from said electron-beam irradiated area of the specimen, and said holding means comprises a transferring casing member engaged at a bottom part of the last stage condenser lens of said lens system in the vicinity of said specimen mounting means, said casing member accommodating therein said scintillator element and being movable in parallel with one of said two directions of movement of said specimen mounting means, and means for movably engaging said casing member to said specimen mounting means to move said member in accordance with movement of said specimen mounting means in said one direction and to hold said member against movement of said specimen mounting means in the other direction of said two orthogonal directions; said apparatus further comprising a photoelectric element for converting light produced by said scintillator element into electrical signals proportional to said light.
 7. An electron beam apparatus as claimed in claim 4, wherein said electron detector means comprises a scintillator element for collecting the electrons advanced from an electron-beam irradiated area of the specimen and a photoelectric element for converting light generated by said scintillator element into electrical signals proportional to said light; said holding means comprising a transferring casing member engaged at a bottom part of the last stage condenser lens of said lens system in the vicinity of said specimen mounting means, said casIng member accommodating therein said scintillator element and said photoelectric element and being movable in parallel with one of said two directions of movement of said specimen mounting means, and means for engaging said casing member to said specimen mounting means to move said member in accordance with movement of said specimen mounting means in said one direction and to hold said member against movement of said specimen mounting means in the other direction of said two orthogonal directions.
 8. An electron beam apparatus as claimed in claim 7, further comprising a light guide composed of flexible optical fibers for conducting the light generated by said scintillator element to said photoelectric element, wherein said photoelectric element is secured to said apparatus.
 9. A electron beam apparatus as claimed in claim 6, wherein said scintillator element includes a metal film coating which forms said electron incident surface of said detector means; and said detector means further comprises means to apply a first positive voltage to said scintillator element and being disposed therearound and an auxiliary electrode being fed at a second positive voltage and being attached at one end of said transferring casing member so as to oppose said electron-beam irradiated area of the specimen, said auxiliary electrode providing an electric-field distribution due to the first positive voltage of said scintillator.
 10. An electron beam apparatus as claimed in claim 7, wherein said transferring casing member is located above said specimen mounting means and below said last stage condenser lens system and on a side of said specimen mounting means at a certain distance therefrom, so that said electron incident surface of said scintillator element does not directly face the irradiated area of the specimen.
 11. An apparatus for bombarding a specimen with an electron-beam and detecting secondary electrons generated by the bombardment: comprising an electron gun; condenser lens means for focusing the electron beam from said electron gun onto a selected area for analysis of the specimen surface, said lens means being disposed as close as possible to the specimen for shortening the focal length of the lens; a specimen stage movable in two directions perpendicular to each other in a plane perpendicular to said beam; a transferring member movably engaged to a bottom part of said condenser lens means in the vicinity of said specimen stage so as to become movable in parallel with one of said two directions; means for engaging said transferring member to said specimen stage to move said member in accordance with movement of said specimen stage in one of said two directions and to hold said member against movement of said specimen stage in the other direction; a scintillator element mounted on said transferring member for collecting incident electrons from the electron-beam irradiated area of the specimen; and a photoelectric element connected to said scintillator element for converting light produced by said scintillator element into an electric signal proportional to said light.
 12. An apparatus for bombarding a specimen with an electron-beam and detecting secondary electrons generated by the bombardment, comprising an electron gun; condenser lens means for focusing the electron beam from said electron gun onto a selected area for analysis on the specimen surface, said lens being disposed as close to the specimen as possible for shortening the focal length of the lens; a specimen stage movable in two perpendicular directions in a plane perpendicular to said beam; transferring means movably engaged to a bottom part of said condenser lens means in the vicinity of said specimen stage so as to become movable in parallel with one of said two directions; means for engaging said transferring means to said specimen stage to move said transferring means in accordance with movement of said specimen stage in one of said two directiOns and hold said transferring means against movement of said specimen stage in the other direction; a scintillator element mounted on said transferring means for collecting incident electrons from the electron-beam irradiated area of the specimen; a photoelectric element secured on said apparatus for converting light produced by said scintillator element into an electric signal proportional to said light; and a light guide including flexible optical fibers for conducting light produced by said scintillator element to said photoelectric element.
 13. An apparatus as claimed in claim 11, wherein said scintillator element is of a metal film coating which forms said electron incident surface of said detector means, further comprising means to apply a first positive voltage to said scintillator element and being disposed therearound and an auxiliary electrode being fed at a second positive voltage attached at one end of said transferring means and opposing said electron-beam irradiated area of he specimen, said auxiliary electrode providing an electric-field distribution by the first positive voltage of said scintillator.
 14. An apparatus as claimed in claim 12, wherein said transferring means comprises cylindrical casing having mounting frames secured therearound and ball bearing rotary members respectively attached to the frames, and rail means attached in parallel with said one of said two directions to said bottom part of said condenser lens means and receiving therein said rotary members whereby said cylindrical casing can travel along said rail means; and said engaging means comprises a U-shaped guide member defining a guide groove and secured in parallel with said other direction to one of said frames, and a strut member disposed on a peripheral part of said specimen stage and slidably engaged in the guide groove of said U-shaped member. 